That stuff is tough as nails; Kudo's for you to take the plunge to try it. J

The problem is that the tap isn't meant for these hard materials; it literally pushed the part apart, rather than cutting it away. Without a special tap, i would cut a 2.7mm hole for tapping. (requires less force to cut the thread) The threads will be less deep, but considering the hardness of the material you don't need to worry. I sometimes use an oversized drill for the tap in aluminum that's less 'willing' to be tapped. With tough materials I use cheap (conrad, lithium) grease instead of oil for cutting.

It would be fair easy to make a motoradapter for that spur from aluminum, loosing the cushion. (it would probably mean less wobbling as well)

I don't know much of metals, but the grainy texture inside means it's sintered I think. Best bet is probably drawing up the part I want and having it made by a CNC service, like Lizard suggested earlier.Do you guys have a recommendation for a good CAD tool for someone without prior CAD experience? Sketchup any good?

@Serum, I would actually like the idea of the cushdrive to have some drivetrain cushening, but you might be right that it will cause wobble. Maybe I just have to settle with the tire-surface contact as the only cushening :).

As long I haven't gotten the XO-1 cushdrive spurs to work, I will be using the OFNA DM-1 spur mount. Those spurs go up to 49T. Later I found the OFNA GTP spurs go up to 51T, but they use a different mounting system. For now I think I'm good with the 49T as that allows gearing between ~150-180 kph nominal no-load with the gears I have, and I'm not sure if the batteries and motor can do much more anyway for continuous use and whether I find enough space to actually use those kind of speeds.

@Lizard, did you try the motor yet in your XO-1?

For the benefit of anyone reading along, here's the OFNA part no. of the alternatives. Both spur mounts have 8 mm bore, so need a reducer for 6 mm motor shafts, like I used in pic above:

But now you're limited to a 49t pinion,do you still want to go with the 54t in the long run?

Yes, you are right; it is sintered material. For CAD, i use solidworks. don't know enough about sketchup..

Thanks, I'll look into Solidworks.

I don't really think 54T is necessary anymore. The need for the big pinion is very specific for the low RPM (900kv, 6S max) of this motor and I could still go a bit down on the spur, to loads that are probably way beyond what the motor will be happy with. I just thought it would be cool to have the cushdrive thing.

Below's an updated gearing matrix, listing no-load wheel-speed (in kph) at nominal Voltage. I need at least 39 mm shaft-to-shaft distance or the motor will rub the rear chassis brace, so red cells are out of the question.

I already have the Aliexpress 30T 6 mm bore pinion, but it's just a huge and clumsy chunk of steel, weighing a whopping 87 g, which is a bit more than I like (complete spool with 36T plastic gear only weighs 56 g). I might also try and bore out a 29T XO-1 pinion I have laying around, material is the same as the cushdrive key, so at least I know what I'm getting myself into :). Kershaw also has some 8 mm bore pinions that would work on the spool shaft with a bore reducer, but he charges $20 intl. shipping even on that small stuff, so that would mean a $40 pinion, which I would like to avoid.

Yeah, I just want to make it as easy on the powerplant as can be, main goal is to have a fast car that can finish a pack without overheating. But you're right, in total the weight of that pinion plus spool shaft will be in the order of a normal center diff with steel gears.

Thanks for the offer! I appreciate that and will keep it in mind. I had some good experiences with LiquidRC before, always good prices and fast shipping to EU.